Superconducting properties of rare-earth boron hydrides at high pressure studied by first-principles calculations

It is a long-thought proposal that dense light-element molecular hydrides, such as diborane (B₂H₆) and methane (CH₄), offer an ideal platform to search for phonon-mediated superconductors. However, these hydrides are often unstable under sufficiently high pressure, e.g., B₂H₆ decomposed into BH and H₂ at pressures of above 153 GPa, which are unlikely to exhibit high superconductivity. Here, we find a feasible route to stabilize these light-element molecular hydrides with high superconductivity under high pressure by high-throughput structure searches and first-principles calculations. We uncover a series of stable H-rich rare-earth (R) metal based boron hydrides RB₂H₁₀ with polydiborane networks. Strikingly, YB₂H₁₀ is predicted to be a high-temperature superconductor with unprecedentedly critical temperature ( Tc ) of up to 93 K under 150 GPa. The present findings open a route to stabilize the unstable diborane by bringing the additional R metals into the lattice under high pressure, as well as tuning the superconductivity among diborane-based hydrides and other similar dense light-element molecular hydrides.